A map-less and camera-based lane markings sampling method for level-3 autonomous driving vehicles

ABSTRACT

A computer-implemented method, apparatus, and system for discretizing lane markings and for generating a lane reference line is disclosed. A polynomial defined over an (x,y) coordinate system is received, the polynomial being representative of at least a portion of a lane boundary line. A length of the polynomial is determined. The polynomial is discretized, comprising determining a plurality of discretization points on the polynomial to represent the polynomial, wherein a first discretization point is a first end of the polynomial, wherein subsequent discretization points are determined successively until the polynomial is completely discretized, and wherein each discretization point other than the first discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point. Thereafter, a lane reference line comprising a plurality of points is generated based on the discretized polynomial.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to operating autonomous vehicles. More particularly, embodiments of the disclosure relate to lane marking sampling for Level 3 autonomous driving.

BACKGROUND

Vehicles operating in an autonomous mode (e.g., driverless) can relieve occupants, especially the driver, from some driving-related responsibilities. When operating in an autonomous mode, the vehicle can navigate to various locations using onboard sensors, allowing the vehicle to travel with minimal human interaction or in some cases without any passengers.

For a map-less and camera-based Level 3 autonomous vehicle, lane marking detection is often carried out by cameras. For instance, a forward-facing camera detects a lane marking ahead, which is represented as polynomials (usually cubic polynomials). In order to process those polynomials properly and to generate a reference line for motion planning, the polynomials need to be discretized.

SUMMARY

In a first aspect, the present disclosure provides a computer-implemented method for operating an autonomous driving vehicle, the method comprising: generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving; discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point; and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.

In a second aspect, the present disclosure provides a non-transitory machine-readable medium having instructions stored therein, which when executed by a processor, cause the processor to perform operations, the operations comprising: generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving; discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point; and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.

In a third aspect, the present disclosure provides a data processing system, comprising: a processor; and a memory coupled to the processor to store instructions, which when executed by the processor, cause the processor to perform operations, the operations including: generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving, discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point, and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are illustrated by way of example and not limitation in the figures of the accompanying drawings in which like references indicate similar elements.

FIG. 1 is a block diagram illustrating a networked system according to one embodiment.

FIG. 2 is a block diagram illustrating an example of an autonomous vehicle according to one embodiment.

FIGS. 3A-3B are block diagrams illustrating an example of a perception and planning system used with an autonomous vehicle according to one embodiment.

FIG. 4 is a block diagram illustrating various components utilized according to one embodiment.

FIG. 5 is a diagram illustrating discretization of a polynomial according to one embodiment.

FIG. 6 is a diagram illustrating generation of a lane reference line according to one embodiment.

FIG. 7 is a flowchart illustrating an example method for discretizing a lane marking polynomial according to one embodiment.

FIG. 8 is a flowchart illustrating an example method for discretizing a lane marking polynomial according to another embodiment.

FIG. 9 is a block diagram illustrating a data processing system according to one embodiment.

DETAILED DESCRIPTION

Various embodiments and aspects of the disclosures will be described with reference to details discussed below, and the accompanying drawings will illustrate the various embodiments. The following description and drawings are illustrative of the disclosure and are not to be construed as limiting the disclosure. Numerous specific details are described to provide a thorough understanding of various embodiments of the present disclosure. However, in certain instances, well-known or conventional details are not described in order to provide a concise discussion of embodiments of the present disclosures.

Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in conjunction with the embodiment can be included in at least one embodiment of the disclosure. The appearances of the phrase “in one embodiment” in various places in the specification do not necessarily all refer to the same embodiment.

One embodiment of the disclosure relates to a computer-implemented method, apparatus, and system for discretizing lane markings and for generating a lane reference line to autonomously drive an autonomous driving vehicle (ADV). A polynomial is obtained representing at least a portion of a lane boundary line of a lane in which the ADV is driving. In one embodiment, the polynomial has been generated based on camera detection of lane markings, without having to use map data associated with the lane. The polynomial is then discretized by sampling some reference points along the polynomial into a number of discretized points. In discretizing the polynomial, the first overall point is selected, for example, at the starting of the polynomial. The subsequent points are sampled or selected based on at least in part on slope its immediate or adjacent preceding point.

The subsequent points are determined for the entire polynomial. In one embodiment, the length of the polynomial is determined using a Gauss-Legendre integration method. In one embodiment, the discretization points are further apart along the polynomial where the slope of the polynomial is smaller, and vice versa. It should be appreciated that selecting the discretization points in this way enables appropriate sampling of the lane markings across various conditions, including straight as well as curved lane markings.

In one embodiment, for each subsequent discretization point i other than the first discretization point, its x-coordinate x_(i) is determined based on a formula x_(i)=x_(i-1)+1/√{square root over (1+(x_(i-1))²)}, where x_(i-1) is an x-coordinate of a previous discretization point, and d(x_(i-1)) represents a slope of the polynomial at the previous discretization point. The slope can be calculated based on a derivative of the polynomial at the point. It should be appreciated that for the polynomial f(x)=ax³+bx²+cx+d, the slope at a given point (x_(i-1), y_(i-1)) is d(x_(i-1))=3ax_(i-1) ²+2bx_(i-1)+c. And the y-coordinate y_(i) for the discretization point i is determined based on its x-coordinate x_(i) and the polynomial (i.e., y_(i)=ax_(i) ³+bx_(i) ²+cx_(i)+d). Thereafter, a lane reference line is generated based on the discretized points of the polynomial. In one embodiment, the lane reference line is generated based on two discretized polynomials representative of both lane boundary lines on both sides of the lane.

FIG. 1 is a block diagram illustrating an autonomous vehicle network configuration according to one embodiment of the disclosure. Referring to FIG. 1, network configuration 100 includes autonomous vehicle 101 that may be communicatively coupled to one or more servers 103-104 over a network 102. Although there is one autonomous vehicle shown, multiple autonomous vehicles can be coupled to each other and/or coupled to servers 103-104 over network 102. Network 102 may be any type of networks such as a local area network (LAN), a wide area network (WAN) such as the Internet, a cellular network, a satellite network, or a combination thereof, wired or wireless. Server(s) 103-104 may be any kind of servers or a cluster of servers, such as Web or cloud servers, application servers, backend servers, or a combination thereof. Servers 103-104 may be data analytics servers, content servers, traffic information servers, map and point of interest (MPOI) servers, or location servers, etc.

An autonomous vehicle refers to a vehicle that can be configured to in an autonomous mode in which the vehicle navigates through an environment with little or no input from a driver. Such an autonomous vehicle can include a sensor system having one or more sensors that are configured to detect information about the environment in which the vehicle operates. The vehicle and its associated controller(s) use the detected information to navigate through the environment. Autonomous vehicle 101 can operate in a manual mode, a full autonomous mode, or a partial autonomous mode.

In one embodiment, autonomous vehicle 101 includes, but is not limited to, perception and planning system 110, vehicle control system 111, wireless communication system 112, user interface system 113, infotainment system 114, and sensor system 115. Autonomous vehicle 101 may further include certain common components included in ordinary vehicles, such as, an engine, wheels, steering wheel, transmission, etc., which may be controlled by vehicle control system 111 and/or perception and planning system 110 using a variety of communication signals and/or commands, such as, for example, acceleration signals or commands, deceleration signals or commands, steering signals or commands, braking signals or commands, etc.

Components 110-115 may be communicatively coupled to each other via an interconnect, a bus, a network, or a combination thereof. For example, components 110-115 may be communicatively coupled to each other via a controller area network (CAN) bus. A CAN bus is a vehicle bus standard designed to allow microcontrollers and devices to communicate with each other in applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles, but is also used in many other contexts.

Referring now to FIG. 2, in one embodiment, sensor system 115 includes, but it is not limited to, one or more cameras 211, global positioning system (GPS) unit 212, inertial measurement unit (IMU) 213, radar unit 214, and a light detection and range (LIDAR) unit 215. GPS system 212 may include a transceiver operable to provide information regarding the position of the autonomous vehicle. IMU unit 213 may sense position and orientation changes of the autonomous vehicle based on inertial acceleration. Radar unit 214 may represent a system that utilizes radio signals to sense objects within the local environment of the autonomous vehicle. In some embodiments, in addition to sensing objects, radar unit 214 may additionally sense the speed and/or heading of the objects. LIDAR unit 215 may sense objects in the environment in which the autonomous vehicle is located using lasers. LIDAR unit 215 could include one or more laser sources, a laser scanner, and one or more detectors, among other system components. Cameras 211 may include one or more devices to capture images of the environment surrounding the autonomous vehicle. Cameras 211 may be still cameras and/or video cameras. A camera may be mechanically movable, for example, by mounting the camera on a rotating and/or tilting a platform.

Sensor system 115 may further include other sensors, such as, a sonar sensor, an infrared sensor, a steering sensor, a throttle sensor, a braking sensor, and an audio sensor (e.g., microphone). An audio sensor may be configured to capture sound from the environment surrounding the autonomous vehicle. A steering sensor may be configured to sense the steering angle of a steering wheel, wheels of the vehicle, or a combination thereof. A throttle sensor and a braking sensor sense the throttle position and braking position of the vehicle, respectively. In some situations, a throttle sensor and a braking sensor may be integrated as an integrated throttle/braking sensor.

In one embodiment, vehicle control system 111 includes, but is not limited to, steering unit 201, throttle unit 202 (also referred to as an acceleration unit), and braking unit 203. Steering unit 201 is to adjust the direction or heading of the vehicle. Throttle unit 202 is to control the speed of the motor or engine that in turn controls the speed and acceleration of the vehicle. Braking unit 203 is to decelerate the vehicle by providing friction to slow the wheels or tires of the vehicle. Note that the components as shown in FIG. 2 may be implemented in hardware, software, or a combination thereof.

Referring back to FIG. 1, wireless communication system 112 is to allow communication between autonomous vehicle 101 and external systems, such as devices, sensors, other vehicles, etc. For example, wireless communication system 112 can wirelessly communicate with one or more devices directly or via a communication network, such as servers 103-104 over network 102. Wireless communication system 112 can use any cellular communication network or a wireless local area network (WLAN), e.g., using WiFi to communicate with another component or system. Wireless communication system 112 could communicate directly with a device (e.g., a mobile device of a passenger, a display device, a speaker within vehicle 101), for example, using an infrared link, Bluetooth, etc. User interface system 113 may be part of peripheral devices implemented within vehicle 101 including, for example, a keyboard, a touch screen display device, a microphone, and a speaker, etc.

Some or all of the functions of autonomous vehicle 101 may be controlled or managed by perception and planning system 110, especially when operating in an autonomous driving mode. Perception and planning system 110 includes the necessary hardware (e.g., processor(s), memory, storage) and software (e.g., operating system, planning and routing programs) to receive information from sensor system 115, control system 111, wireless communication system 112, and/or user interface system 113, process the received information, plan a route or path from a starting point to a destination point, and then drive vehicle 101 based on the planning and control information. Alternatively, perception and planning system 110 may be integrated with vehicle control system 111.

For example, a user as a passenger may specify a starting location and a destination of a trip, for example, via a user interface. Perception and planning system 110 obtains the trip related data. For example, perception and planning system 110 may obtain location and route information from an MPOI server, which may be a part of servers 103-104. The location server provides location services and the MPOI server provides map services and the POIs of certain locations. Alternatively, such location and MPOI information may be cached locally in a persistent storage device of perception and planning system 110.

While autonomous vehicle 101 is moving along the route, perception and planning system 110 may also obtain real-time traffic information from a traffic information system or server (TIS). Note that servers 103-104 may be operated by a third party entity. Alternatively, the functionalities of servers 103-104 may be integrated with perception and planning system 110. Based on the real-time traffic information, MPOI information, and location information, as well as real-time local environment data detected or sensed by sensor system 115 (e.g., obstacles, objects, nearby vehicles), perception and planning system 110 can plan an optimal route and drive vehicle 101, for example, via control system 111, according to the planned route to reach the specified destination safely and efficiently.

Server 103 may be a data analytics system to perform data analytics services for a variety of clients. In one embodiment, data analytics system 103 includes data collector 121 and machine learning engine 122. Data collector 121 collects driving statistics 123 from a variety of vehicles, either autonomous vehicles or regular vehicles driven by human drivers. Driving statistics 123 include information indicating the driving commands (e.g., throttle, brake, steering commands) issued and responses of the vehicles (e.g., speeds, accelerations, decelerations, directions) captured by sensors of the vehicles at different points in time. Driving statistics 123 may further include information describing the driving environments at different points in time, such as, for example, routes (including starting and destination locations), MPOIs, road conditions, weather conditions, etc.

Based on driving statistics 123, machine learning engine 122 generates or trains a set of rules, algorithms, and/or predictive models 124 for a variety of purposes. In one embodiment, algorithms 124 may include algorithms for processing lane markings based on camera data. Algorithms 124 can then be uploaded on ADVs to be utilized during autonomous driving in real-time.

FIGS. 3A and 3B are block diagrams illustrating an example of a perception and planning system used with an autonomous vehicle according to one embodiment. System 300 may be implemented as a part of autonomous vehicle 101 of FIG. 1 including, but is not limited to, perception and planning system 110, control system 111, and sensor system 115. Referring to FIGS. 3A-3B, perception and planning system 110 includes, but is not limited to, localization module 301, perception module 302, prediction module 303, decision module 304, planning module 305, control module 306, routing module 307, and polynomial discretization module 308.

Some or all of modules 301-308 may be implemented in software, hardware, or a combination thereof. For example, these modules may be installed in persistent storage device 352, loaded into memory 351, and executed by one or more processors (not shown). Note that some or all of these modules may be communicatively coupled to or integrated with some or all modules of vehicle control system 111 of FIG. 2. Some of modules 301-308 may be integrated together as an integrated module.

Localization module 301 determines a current location of autonomous vehicle 300 (e.g., leveraging GPS unit 212) and manages any data related to a trip or route of a user. Localization module 301 (also referred to as a map and route module) manages any data related to a trip or route of a user. A user may log in and specify a starting location and a destination of a trip, for example, via a user interface. Localization module 301 communicates with other components of autonomous vehicle 300, such as map and route information 311, to obtain the trip related data. For example, localization module 301 may obtain location and route information from a location server and a map and POI (MPOI) server. A location server provides location services and an MPOI server provides map services and the POIs of certain locations, which may be cached as part of map and route information 311. While autonomous vehicle 300 is moving along the route, localization module 301 may also obtain real-time traffic information from a traffic information system or server.

Based on the sensor data provided by sensor system 115 and localization information obtained by localization module 301, a perception of the surrounding environment is determined by perception module 302. The perception information may represent what an ordinary driver would perceive surrounding a vehicle in which the driver is driving. The perception can include the lane configuration, traffic light signals, a relative position of another vehicle, a pedestrian, a building, crosswalk, or other traffic related signs (e.g., stop signs, yield signs), etc., for example, in a form of an object. The lane configuration includes information describing a lane or lanes, such as, for example, a shape of the lane (e.g., straight or curvature), a width of the lane, how many lanes in a road, one-way or two-way lane, merging or splitting lanes, exiting lane, etc.

Perception module 302 may include a computer vision system or functionalities of a computer vision system to process and analyze images captured by one or more cameras in order to identify objects and/or features in the environment of autonomous vehicle. The objects can include traffic signals, road way boundaries, other vehicles, pedestrians, and/or obstacles, etc. The computer vision system may use an object recognition algorithm, video tracking, and other computer vision techniques. In some embodiments, the computer vision system can map an environment, track objects, and estimate the speed of objects, etc. Perception module 302 can also detect objects based on other sensors data provided by other sensors such as a radar and/or LIDAR.

For each of the objects, prediction module 303 predicts what the object will behave under the circumstances. The prediction is performed based on the perception data perceiving the driving environment at the point in time in view of a set of map/rout information 311 and traffic rules 312. For example, if the object is a vehicle at an opposing direction and the current driving environment includes an intersection, prediction module 303 will predict whether the vehicle will likely move straight forward or make a turn. If the perception data indicates that the intersection has no traffic light, prediction module 303 may predict that the vehicle may have to fully stop prior to enter the intersection. If the perception data indicates that the vehicle is currently at a left-turn only lane or a right-turn only lane, prediction module 303 may predict that the vehicle will more likely make a left turn or right turn respectively.

For each of the objects, decision module 304 makes a decision regarding how to handle the object. For example, for a particular object (e.g., another vehicle in a crossing route) as well as its metadata describing the object (e.g., a speed, direction, turning angle), decision module 304 decides how to encounter the object (e.g., overtake, yield, stop, pass). Decision module 304 may make such decisions according to a set of rules such as traffic rules or driving rules 312, which may be stored in persistent storage device 352.

Routing module 307 is configured to provide one or more routes or paths from a starting point to a destination point. For a given trip from a start location to a destination location, for example, received from a user, routing module 307 obtains route and map information 311 and determines all possible routes or paths from the starting location to reach the destination location. Routing module 307 may generate a reference line in a form of a topographic map for each of the routes it determines from the starting location to reach the destination location. A reference line refers to an ideal route or path without any interference from others such as other vehicles, obstacles, or traffic condition. That is, if there is no other vehicle, pedestrians, or obstacles on the road, an ADV should exactly or closely follows the reference line. The topographic maps are then provided to decision module 304 and/or planning module 305. Decision module 304 and/or planning module 305 examine all of the possible routes to select and modify one of the most optimal routes in view of other data provided by other modules such as traffic conditions from localization module 301, driving environment perceived by perception module 302, and traffic condition predicted by prediction module 303. The actual path or route for controlling the ADV may be close to or different from the reference line provided by routing module 307 dependent upon the specific driving environment at the point in time.

Based on a decision for each of the objects perceived, planning module 305 plans a path or route for the autonomous vehicle, as well as driving parameters (e.g., distance, speed, and/or turning angle), using a reference line provided by routing module 307 as a basis. That is, for a given object, decision module 304 decides what to do with the object, while planning module 305 determines how to do it. For example, for a given object, decision module 304 may decide to pass the object, while planning module 305 may determine whether to pass on the left side or right side of the object. Planning and control data is generated by planning module 305 including information describing how vehicle 300 would move in a next moving cycle (e.g., next route/path segment). For example, the planning and control data may instruct vehicle 300 to move 10 meters at a speed of 30 mile per hour (mph), then change to a right lane at the speed of 25 mph.

Based on the planning and control data, control module 306 controls and drives the autonomous vehicle, by sending proper commands or signals to vehicle control system 111, according to a route or path defined by the planning and control data. The planning and control data include sufficient information to drive the vehicle from a first point to a second point of a route or path using appropriate vehicle settings or driving parameters (e.g., throttle, braking, steering commands) at different points in time along the path or route.

In one embodiment, the planning phase is performed in a number of planning cycles, also referred to as driving cycles, such as, for example, in every time interval of 100 milliseconds (ms). For each of the planning cycles or driving cycles, one or more control commands will be issued based on the planning and control data. That is, for every 100 ms, planning module 305 plans a next route segment or path segment, for example, including a target position and the time required for the ADV to reach the target position. Alternatively, planning module 305 may further specify the specific speed, direction, and/or steering angle, etc. In one embodiment, planning module 305 plans a route segment or path segment for the next predetermined period of time such as 5 seconds. For each planning cycle, planning module 305 plans a target position for the current cycle (e.g., next 5 seconds) based on a target position planned in a previous cycle. Control module 306 then generates one or more control commands (e.g., throttle, brake, steering control commands) based on the planning and control data of the current cycle.

Note that decision module 304 and planning module 305 may be integrated as an integrated module. Decision module 304/planning module 305 may include a navigation system or functionalities of a navigation system to determine a driving path for the autonomous vehicle. For example, the navigation system may determine a series of speeds and directional headings to affect movement of the autonomous vehicle along a path that substantially avoids perceived obstacles while generally advancing the autonomous vehicle along a roadway-based path leading to an ultimate destination. The destination may be set according to user inputs via user interface system 113. The navigation system may update the driving path dynamically while the autonomous vehicle is in operation. The navigation system can incorporate data from a GPS system and one or more maps so as to determine the driving path for the autonomous vehicle.

FIG. 4 is a block diagram 400 illustrating various components utilized according to one embodiment. Camera 211 captures the lane markings (e.g., lane boundary lines in the front of the autonomous vehicle). The camera 211 may include or be coupled to a lane marking detection module (which may be implemented as a part of perception module 302), which generates polynomials representative of the lane boundary lines. The boundary line polynomials are input into the polynomial discretization module 308, which discretizes the boundary line polynomials. The discretized boundary line(s) are forwarded to a reference line generation module 430, where the lane reference line is generated. Note that the polynomial discretization module 308 may be integrated as a part of reference line generation module 430. Reference line generation module 430 may also be integrated as a part of routing module 307.

In one embodiment, perception module 302 generates a polynomial representing at least a portion of a lane boundary line of a lane in which the ADV is driving, based on camera data obtained from a camera. In one embodiment, the polynomial has been generated based on camera detection of lane markings. In one embodiment, the polynomial is a cubic polynomial (i.e., the polynomial may be in a form of f(x)=ax³+bx²+cx+d). A length of the polynomial is determined, which may determined using a Gauss-Legendre integration method.

The polynomial is then discretized by polynomial discretization module 308 according to the length of the polynomial. The discretizing of the polynomial includes determining a plurality of discretization points on the polynomial to represent the polynomial. A first discretization point may be determined at a first end of the polynomial (e.g., starting point of the polynomial). Subsequent discretization points may be determined successively until the polynomial is completely discretized. Each successive discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point (e.g., an immediately or adjacent preceding point). In one embodiment, the discretization points are further apart along the polynomial if the slope of the polynomial is smaller, and vice versa. It should be appreciated that selecting the discretization points in this way enables appropriate sampling of the lane markings across various conditions, including straight as well as curved lane markings.

In one embodiment, for each subsequent discretization point i other than the first discretization point, its x-coordinate x_(i) is determined based on a formula x_(i)=x_(i-1)+1/√{square root over (1+d(x_(i-1))²)}, where x_(i-1) is an x-coordinate of a previous discretization point, and d(x_(i-1)) is a slope of the polynomial at the previous discretization point. The slope can be calculated based on a derivative of the polynomial at the point. It should be appreciated that for the polynomial of f(x)=ax³+bx²+cx+d, the slope at a given point (x_(i-1), y_(i-1)) is d(x_(i-1))=3ax_(i-1) ²+2bx_(i-1)+c. The y-coordinate y_(i) for the discretization point i is determined based on its x-coordinate x_(i) and the polynomial (i.e., y_(i)=ax_(i) ³+bx_(i) ²+cx_(i)+d). Thereafter, a lane reference line is generated by reference line generation module 430 based on the discretized points of the polynomial. In one embodiment, the lane reference line is generated based on two discretized polynomials representative of both lane boundary lines on both sides of the lane. The reference line is then utilized by planning module 305 to plan a trajectory to drive the vehicle to drive along the lane.

FIG. 5 is a diagram 500 illustrating discretization of a polynomial according to one embodiment. A lane boundary line polynomial 510 is to be discretized into discretization points 520A-520G using at least some of the techniques described above. In other words, a plurality of discretization points 520A-520G on the polynomial 510 are determined to represent the polynomial 510. The discretization step size is inversely correlated with the sloped of the polynomial 510. In other words, the discretization points 520A-520G are further apart along the polynomial 510 where the slope of the polynomial 510 is smaller, and vice versa. It should be appreciated that selecting the discretization points 520A-520G in this way enables appropriate sampling of the lane markings across various conditions, including straight as well as curved lane markings.

FIG. 6 is a diagram 600 illustrating generation of a lane reference line according to one embodiment. A lane reference line 620 is generated based on the lane boundary line 610 (which can be discretized as described above). A lane reference line may be close to a center line of the lane. Generation of the lane reference line 620 segments that correspond to segments ab and bc (a−b−c) of the lane boundary line 610 is described for illustrative purposes. A segment a₁b_(a) is generated based on the segment ab, where segments a₁b_(a) and ab are parallel to each other, the length of the segment alba is equal to the length of the segment ab, the distance between the segments a₁b_(a) and ab is half the lane width, and the segment a₁b_(a) is perpendicular to a line that connects b and b_(a). Similarly, a segment b_(c)c₁ is generated based on the segment bc, where segments b_(c)c₁ and bc are parallel to each other, the length of the segment b_(c)c₁ is equal to the length of the segment bc, the distance between the segments b_(c)c₁ and bc is half the lane width, and the segment b_(c)c₁ is perpendicular to a line that connects b and b_(c). Further, b₁ is the point of intersection between segments a₁b_(a) and b_(c)c₁. Thus, segments a₁−b₁−c₁ represent the portion of the lane reference line 620 that corresponds to the segments a−b−c on the lane boundary line 610. It should be appreciated that the constructed segments a₁−b₁−c₁ possess the following characteristic: the curvature of the segments a₁−b₁−c₁ C(ab₁c₁) is the curvature of the segments a−b−c C(abc) minus half the road width d, that is, C(a₁b₁c₁)=C(abc)−d. This characteristic ensures the reference line constructed from boundary line(s) preserves the shape of the road.

Another reference line comprising segments a₂−b₂−c₂ can be constructed from the other boundary line on the other side of the lane. In a perfect situation, segments a₁−b₁−c₁ and a₂−b₂−c₂ should coincide. However, due to sensor noises and the imperfection of the roadway, the two reference lines generated respectively from the two lane boundary lines almost never completely match. In one embodiment, a weighted reference line may be determined: e.g., a_(w)−b_(w)−c_(w)=w*(a₁−b₁−c₁)+(1−w)*(a₂−b₂−c₂). The weight w can be adjusted empirically according to different sensor systems. In one embodiment, the weight w may be 0.5.

FIG. 7 is a flowchart illustrating an example method 700 for discretizing a lane marking polynomial and generating a lane reference line according to one embodiment. Method 700 may be performed by processing logic which may include software, hardware, or a combination thereof. For example, method 700 may be performed by system 400 of FIG. 4. Referring to FIG. 7, at block 701, processing logic generates a polynomial representing at least a portion of a lane boundary line of a lane in which an ADV is moving. The polynomial may be generated based on image data obtained from one or more cameras mounted on the ADV capturing lane markings of the lane, without having to use map data associated with the lane. At block 702, processing logic discretizes the polynomial into a number of discretized points along the polynomial, including selecting a first overall point, for example, at the start of the polynomial. At block 703, processing iteratively samples subsequent points after the first overall point. Each of the subsequent points is selected based on the slope of the immediate preceding point, for example, using a predetermined formula as described above. Thereafter, at block 704, a lane reference line is generated based on the discretized points of the polynomial. The reference line is utilized in planning a trajectory to drive the ADV to navigate within the lane.

FIG. 8 is a flow diagram illustrating a process of discretizing a polynomial according to one embodiment. Process 800 may be performed by processing logic which may include software, hardware, and a combination thereof. Referring to FIG. 8, in response to a polynomial generated based on camera data, at block 801, the length of the polynomial is determined, for example, using a Gauss Legendre integration method. At block 802, a first discretized point is selected, for example, at the beginning of the polynomial and the slope of the first point is calculated, for example, based on a derivative of the first point. For each of the subsequent points, an iterative process is performed. For example, given a cubic polynomial f(x)=ax³+bx²+cx+d, the slope at the first point (x₀, y₀) can be calculated as d(x₀)=3ax₀ ²+2bx₀+c. Within the iteration, at block 803, the coordinates of a current point (x₁, y₁) of the polynomial is determined based on the coordinates and the slope of a preceding point of a prior iteration. For example, according to one embodiment, x₁=x₀+1/√{square root over (1+d(x₀)²)} and y₁=ax₁ ³+bx₁ ²+cx₁+d. For the initial current point (x₁, y₁), the preceding point is the first overall point (x₀, y₀) determined at block 802. Similarly, x₂=x₁+1/√{square root over (1+d(x₁)²)}, and y₂=ax₂ ³+bx₂ ²+cx₂+d, and so on. At block 804, a slope of the current point is calculated. At block 805, it is determined whether there are more points to be processed, for example, based on the length of the polynomial determined at block 801. If so, at block 806, the current point is designated as the preceding point and a next point becomes the current point, and the above iterative process in blocks 803-804 is repeatedly performed until the entire polynomial has been processed.

Note that some or all of the components as shown and described above may be implemented in software, hardware, or a combination thereof. For example, such components can be implemented as software installed and stored in a persistent storage device, which can be loaded and executed in a memory by a processor (not shown) to carry out the processes or operations described throughout this application. Alternatively, such components can be implemented as executable code programmed or embedded into dedicated hardware such as an integrated circuit (e.g., an application specific IC or ASIC), a digital signal processor (DSP), or a field programmable gate array (FPGA), which can be accessed via a corresponding driver and/or operating system from an application. Furthermore, such components can be implemented as specific hardware logic in a processor or processor core as part of an instruction set accessible by a software component via one or more specific instructions.

FIG. 9 is a block diagram illustrating an example of a data processing system which may be used with one embodiment of the disclosure. For example, system 1500 may represent any of data processing systems described above performing any of the processes or methods described above, such as, for example, perception and planning system 110 or any of servers 103-104 of FIG. 1. System 1500 can include many different components. These components can be implemented as integrated circuits (ICs), portions thereof, discrete electronic devices, or other modules adapted to a circuit board such as a motherboard or add-in card of the computer system, or as components otherwise incorporated within a chassis of the computer system.

Note also that system 1500 is intended to show a high level view of many components of the computer system. However, it is to be understood that additional components may be present in certain implementations and furthermore, different arrangement of the components shown may occur in other implementations. System 1500 may represent a desktop, a laptop, a tablet, a server, a mobile phone, a media player, a personal digital assistant (PDA), a Smartwatch, a personal communicator, a gaming device, a network router or hub, a wireless access point (AP) or repeater, a set-top box, or a combination thereof. Further, while only a single machine or system is illustrated, the term “machine” or “system” shall also be taken to include any collection of machines or systems that individually or jointly execute a set (or multiple sets) of instructions to perform any one or more of the methodologies discussed herein.

In one embodiment, system 1500 includes processor 1501, memory 1503, and devices 1505-1508 connected via a bus or an interconnect 1510. Processor 1501 may represent a single processor or multiple processors with a single processor core or multiple processor cores included therein. Processor 1501 may represent one or more general-purpose processors such as a microprocessor, a central processing unit (CPU), or the like. More particularly, processor 1501 may be a complex instruction set computing (CISC) microprocessor, reduced instruction set computing (RISC) microprocessor, very long instruction word (VLIW) microprocessor, or processor implementing other instruction sets, or processors implementing a combination of instruction sets. Processor 1501 may also be one or more special-purpose processors such as an application specific integrated circuit (ASIC), a cellular or baseband processor, a field programmable gate array (FPGA), a digital signal processor (DSP), a network processor, a graphics processor, a communications processor, a cryptographic processor, a co-processor, an embedded processor, or any other type of logic capable of processing instructions.

Processor 1501, which may be a low power multi-core processor socket such as an ultra-low voltage processor, may act as a main processing unit and central hub for communication with the various components of the system. Such processor can be implemented as a system on chip (SoC). Processor 1501 is configured to execute instructions for performing the operations and steps discussed herein. System 1500 may further include a graphics interface that communicates with optional graphics subsystem 1504, which may include a display controller, a graphics processor, and/or a display device.

Processor 1501 may communicate with memory 1503, which in one embodiment can be implemented via multiple memory devices to provide for a given amount of system memory. Memory 1503 may include one or more volatile storage (or memory) devices such as random access memory (RAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), static RAM (SRAM), or other types of storage devices. Memory 1503 may store information including sequences of instructions that are executed by processor 1501, or any other device. For example, executable code and/or data of a variety of operating systems, device drivers, firmware (e.g., input output basic system or BIOS), and/or applications can be loaded in memory 1503 and executed by processor 1501. An operating system can be any kind of operating systems, such as, for example, Robot Operating System (ROS), Windows operating system from Microsoft®, Mac OS®/iOS® from Apple, Android® from Google®, LINUX, UNIX, or other real-time or embedded operating systems.

System 1500 may further include IO devices such as devices 1505-1508, including network interface device(s) 1505, optional input device(s) 1506, and other optional IO device(s) 1507. Network interface device 1505 may include a wireless transceiver and/or a network interface card (NIC). The wireless transceiver may be a WiFi transceiver, an infrared transceiver, a Bluetooth transceiver, a WiMax transceiver, a wireless cellular telephony transceiver, a satellite transceiver (e.g., a global positioning system (GPS) transceiver), or other radio frequency (RF) transceivers, or a combination thereof. The NIC may be an Ethernet card.

Input device(s) 1506 may include a mouse, a touch pad, a touch sensitive screen (which may be integrated with display device 1504), a pointer device such as a stylus, and/or a keyboard (e.g., physical keyboard or a virtual keyboard displayed as part of a touch sensitive screen). For example, input device 1506 may include a touch screen controller coupled to a touch screen. The touch screen and touch screen controller can, for example, detect contact and movement or break thereof using any of a plurality of touch sensitivity technologies, including but not limited to capacitive, resistive, infrared, and surface acoustic wave technologies, as well as other proximity sensor arrays or other elements for determining one or more points of contact with the touch screen.

IO devices 1507 may include an audio device. An audio device may include a speaker and/or a microphone to facilitate voice-enabled functions, such as voice recognition, voice replication, digital recording, and/or telephony functions. Other IO devices 1507 may further include universal serial bus (USB) port(s), parallel port(s), serial port(s), a printer, a network interface, a bus bridge (e.g., a PCI-PCI bridge), sensor(s) (e.g., a motion sensor such as an accelerometer, gyroscope, a magnetometer, a light sensor, compass, a proximity sensor, etc.), or a combination thereof. Devices 1507 may further include an imaging processing subsystem (e.g., a camera), which may include an optical sensor, such as a charged coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS) optical sensor, utilized to facilitate camera functions, such as recording photographs and video clips. Certain sensors may be coupled to interconnect 1510 via a sensor hub (not shown), while other devices such as a keyboard or thermal sensor may be controlled by an embedded controller (not shown), dependent upon the specific configuration or design of system 1500.

To provide for persistent storage of information such as data, applications, one or more operating systems and so forth, a mass storage (not shown) may also couple to processor 1501. In various embodiments, to enable a thinner and lighter system design as well as to improve system responsiveness, this mass storage may be implemented via a solid state device (SSD). However in other embodiments, the mass storage may primarily be implemented using a hard disk drive (HDD) with a smaller amount of SSD storage to act as a SSD cache to enable non-volatile storage of context state and other such information during power down events so that a fast power up can occur on re-initiation of system activities. Also a flash device may be coupled to processor 1501, e.g., via a serial peripheral interface (SPI). This flash device may provide for non-volatile storage of system software, including BIOS as well as other firmware of the system.

Storage device 1508 may include computer-accessible storage medium 1509 (also known as a machine-readable storage medium or a computer-readable medium) on which is stored one or more sets of instructions or software (e.g., module, unit, and/or logic 1528) embodying any one or more of the methodologies or functions described herein. Processing module/unit/logic 1528 may represent any of the components described above, such as, for example, planning module 305, control module 306, polynomial discretization module 308. Processing module/unit/logic 1528 may also reside, completely or at least partially, within memory 1503 and/or within processor 1501 during execution thereof by data processing system 1500, memory 1503 and processor 1501 also constituting machine-accessible storage media. Processing module/unit/logic 1528 may further be transmitted or received over a network via network interface device 1505.

Computer-readable storage medium 1509 may also be used to store the some software functionalities described above persistently. While computer-readable storage medium 1509 is shown in an exemplary embodiment to be a single medium, the term “computer-readable storage medium” should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, and/or associated caches and servers) that store the one or more sets of instructions. The terms “computer-readable storage medium” shall also be taken to include any medium that is capable of storing or encoding a set of instructions for execution by the machine and that cause the machine to perform any one or more of the methodologies of the present disclosure. The term “computer-readable storage medium” shall accordingly be taken to include, but not be limited to, solid-state memories, and optical and magnetic media, or any other non-transitory machine-readable medium.

Processing module/unit/logic 1528, components and other features described herein can be implemented as discrete hardware components or integrated in the functionality of hardware components such as ASICS, FPGAs, DSPs or similar devices. In addition, processing module/unit/logic 1528 can be implemented as firmware or functional circuitry within hardware devices. Further, processing module/unit/logic 1528 can be implemented in any combination hardware devices and software components.

Note that while system 1500 is illustrated with various components of a data processing system, it is not intended to represent any particular architecture or manner of interconnecting the components; as such details are not germane to embodiments of the present disclosure. It will also be appreciated that network computers, handheld computers, mobile phones, servers, and/or other data processing systems which have fewer components or perhaps more components may also be used with embodiments of the disclosure.

Some portions of the preceding detailed descriptions have been presented in terms of algorithms and symbolic representations of operations on data bits within a computer memory. These algorithmic descriptions and representations are the ways used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. An algorithm is here, and generally, conceived to be a self-consistent sequence of operations leading to a desired result. The operations are those requiring physical manipulations of physical quantities.

It should be borne in mind, however, that all of these and similar terms are to be associated with the appropriate physical quantities and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the above discussion, it is appreciated that throughout the description, discussions utilizing terms such as those set forth in the claims below, refer to the action and processes of a computer system, or similar electronic computing device, that manipulates and transforms data represented as physical (electronic) quantities within the computer system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission or display devices.

Embodiments of the disclosure also relate to an apparatus for performing the operations herein. Such a computer program is stored in a non-transitory computer readable medium. A machine-readable medium includes any mechanism for storing information in a form readable by a machine (e.g., a computer). For example, a machine-readable (e.g., computer-readable) medium includes a machine (e.g., a computer) readable storage medium (e.g., read only memory (“ROM”), random access memory (“RAM”), magnetic disk storage media, optical storage media, flash memory devices).

The processes or methods depicted in the preceding figures may be performed by processing logic that comprises hardware (e.g. circuitry, dedicated logic, etc.), software (e.g., embodied on a non-transitory computer readable medium), or a combination of both. Although the processes or methods are described above in terms of some sequential operations, it should be appreciated that some of the operations described may be performed in a different order. Moreover, some operations may be performed in parallel rather than sequentially.

Embodiments of the present disclosure are not described with reference to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of embodiments of the disclosure as described herein.

In the foregoing specification, embodiments of the disclosure have been described with reference to specific exemplary embodiments thereof. It will be evident that various modifications may be made thereto without departing from the broader spirit and scope of the disclosure as set forth in the following claims. The specification and drawings are, accordingly, to be regarded in an illustrative sense rather than a restrictive sense. 

What is claimed is:
 1. A computer-implemented method for operating an autonomous driving vehicle, the method comprising: generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving; discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point; and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.
 2. The method of claim 1, wherein the polynomial is generated based on camera data obtained from a camera mounted on the ADV capturing the lane without using map data corresponding to the lane.
 3. The method of claim 1, wherein the polynomial is a cubic polynomial.
 4. The method of claim 1, further comprising determining a length of the polynomial using a Gauss-Legendre integration method, wherein the subsequent discretization points are successively determined based on the length of the polynomial.
 5. The method of claim 1, wherein the discretization points are further apart along the polynomial where the slope of the polynomial is smaller, and vice versa.
 6. The method of claim 1, wherein for each successive discretization point i, its x-coordinate x_(i) is determined based on a formula of x_(i)=x_(i-1)+1/√{square root over (1+d(x_(i-1))²)}, where x_(i-1) is an x-coordinate of a previous discretization point, and d(x_(i-1)) is a slope of the polynomial at the previous discretization point.
 7. The method of claim 6, wherein for the successive discretization point i, its y-coordinate y_(i) is determined based on its x-coordinate x_(i) and the polynomial.
 8. The method of claim 1, wherein the lane reference line is generated based on two discretized polynomials representative of both lane boundary lines of the lane.
 9. A non-transitory machine-readable medium having instructions stored therein, which when executed by a processor, cause the processor to perform operations, the operations comprising: generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving; discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point; and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.
 10. The machine-readable medium of claim 9, wherein the polynomial is generated based on camera data obtained from a camera mounted on the ADV capturing the lane without using map data corresponding to the lane.
 11. The machine-readable medium of claim 9, wherein the polynomial is a cubic polynomial.
 12. The machine-readable medium of claim 9, wherein the operations further comprise determining a length of the polynomial using a Gauss-Legendre integration method, wherein the subsequent discretization points are successively determined based on the length of the polynomial.
 13. The machine-readable medium of claim 9, wherein the discretization points are further apart along the polynomial where the slope of the polynomial is smaller, and vice versa.
 14. The machine-readable medium of claim 9, wherein for each successive discretization point i, its x-coordinate x_(i) is determined based on a formula of x_(i)=x_(i-1)+1/√{square root over (1+d(x_(i-1))²)}, where x_(i-1) is an x-coordinate of a previous discretization point, and d(x_(i-1)) is a slope of the polynomial at the previous discretization point.
 15. The machine-readable medium of claim 14, wherein for the successive discretization point i, its y-coordinate y_(i) is determined based on its x-coordinate x_(i) and the polynomial.
 16. The machine-readable medium of claim 9, wherein the lane reference line is generated based on two discretized polynomials representative of both lane boundary lines of the lane.
 17. A data processing system, comprising: a processor; and a memory coupled to the processor to store instructions, which when executed by the processor, cause the processor to perform operations, the operations including generating a polynomial representing at least a portion of a lane boundary line of a lane in which an autonomous driving vehicle (ADV) is moving, discretizing the polynomial into a plurality of discretization points along the polynomial, including determining a first discretization point disposed on a first end of the polynomial, and successively determining subsequent discretization points along the polynomial, wherein each subsequent discretization point is determined based at least in part on a slope of the polynomial at a previous discretization point, and generating a lane reference line based on the discretization points of the polynomial, wherein the lane reference line is utilized to plan a trajectory to drive the ADV within the lane.
 18. The system of claim 17, wherein the polynomial is generated based on camera data obtained from a camera mounted on the ADV capturing the lane without using map data corresponding to the lane.
 19. The system of claim 17, wherein the polynomial is a cubic polynomial.
 20. The system of claim 17, wherein the operations further comprise determining a length of the polynomial using a Gauss-Legendre integration method, wherein the subsequent discretization points are successively determined based on the length of the polynomial. 